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How to build a stable wormhole with dark alien allies

By Jacob Aron

DARK energy just opened a can of wormholes. An extension of Einstein’s gravity may explain this strange force and give us stable wormholes to navigate quickly through the cosmos – but there is a catch.

Building one of these cosmic shortcuts would require talking with aliens made of exotic matter, who can only send us messages via space-time ripples called gravitational waves.

The universe is expanding at ever-increasing speeds, and the prevailing theory is that a mysterious force called dark energy is driving it. But Manuel Hohmann at the University of Tartu in Estonia has been working on an alternative called multimetric gravity, which involves copies of the standard model of particle physics that each have slightly different properties.

Particles within a copy interact with each other as usual to build matter. But those from different copies would only interact via gravity, and they would repel rather than attract each other. If galaxies made from repulsive matter exist between our regular galaxies, that could explain the expansion flinging them apart.

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A version of gravity that involves repulsive matter would allow us to build a stable wormhole

The theory could also generate wormholes, says Hohmann. Most schemes to make stable wormholes require matter with negative energy – something we have never seen. But if a wormhole is built with equal amounts of regular and repulsive matter, that would hold it open (Physical Review D, doi.org/sdz).

To build one, civilisations made from each type of matter would need to cooperate and they could only talk via gravitational waves.

Hohmann accepts this scenario has its difficulties. But if dark galaxies are out there, he thinks we can find them. Normal galaxies warp space-time in a way that can magnify light from objects behind them. A dark galaxy would defocus light, creating a faint smudge that future telescopes may be able to spot.

This article appeared in print under the headline “Ask ET to help build a working wormhole”